Abstract:
Mass spectrometry is one of the most critical chemical technique for the identification of unknown chemicals. Conventional mass spectrometers measure the mass-to-charge ratio of molecules and use sophisticated algorithms based on charge and isotope distribution to reverse calculate the mass of the molecule. Measurements of the mass-to-charge ratio of a molecule works perfectly for small molecules, since the charge that can be placed on a unit mass can be large and the resulting ions have strong interactions with the electrical and magnetic fields used in conventional mass spectrometers. On the other hand, conventional mass spectrometry faces difficulties in analyzing large molecules, nanoparticles and biostructures since the mass-to-charge ratio of these entities are typically much larger. Here we propose a new paradigm for accomplishing top-down mass spectrometry at this high-mass regime by using nanoelectromechanical systems (NEMS). NEMS sensors are tiny mechanical resonators that can be controlled electronically. Due to their small mass, they are extremely sensitive to added mass: indeed, it is possible to obtain 10kDa mass resolution with Silicon-based and 1Da mass resolution with carbon nanotube based NEMS devices. NEMS devices measure the mass of a molecule directly, i.e. there is no need to put excess charge on a molecule. For these reasons, it is possible to perform neutral molecule mass spectrometry with NEMS devices. Moreover, very heavy entities, such as nanoparticles and organelles, can be analyzed by NEMS since the mass resolution does not degrade with increasing mass unlike conventional mass spectrometry. In this colloquium talk, I will compile our experiments over the several years for the implementation of neutral, Mega-Dalton range mass spectrometry with NEMS technology.